Methods and compositions for inhibiting plant growth

ABSTRACT

THE PRESENT INVENTION IS CONCERNED WITH METHODS AND COMPOSITIONS USEFUL IN INHIBITING THE GROWTH OF PLANTS, AND IS PARTICULARLY DIRECTED TO METHODS EMPLOYING AND COMPOSITIONS COMPRISING AN ACTIVE AGENT WHICH IS A COMPOUND OF THE FORMULA   2-R&#39;&#39;,3-C6H5,(R-)N-QUINOXALINE   OR ITS ACID ADDITION SALTS, WHEREIN R REPRESENTS HALO OR METHYL, SAID R BEING LOCATED ON THE 6 OR 7 POSITION, ONLY; R&#39;&#39; REPRESENTS HALO, HYDROXY, LOWERALKOXY, AMINO, N-LOWERALKYLAMINO, DI-N-LOWERALKYLAMINO, OR PIPERIDINO; AND NREPRESENTS AN INTEGER OF FROM 0 TO 1, BOTH INCLUSIVE. THE PRESENT INVENTION IS ALSO DIRECTED TO THE NOVEL COMPOUND OF THE FORMULA   2-(PIPERIDIN-1-YL),3-C6H5,(R-)N-QUINOXALINE   AND ITS ACID ADDITION SALTS, WHEREIN R, AS ABOVE, REPRESENTS HALO OR METHYL, SAID R BEING LOCATED ON THE 6 OR 7 POSITION, ONLY, AND N REPRESENTS AN INTEGER OF FROM 0 TO 1, BOTH INCLUSIVE.

United States Patent 3,582,315 METHODS AND COMPOSITIONS FOR INHIBITING PLANT GROWTH Quentin Francis Soper, Indianapolis, Ind., assignor to Eli Lilly and Company, Indianapolis, Ind. No Drawing. Filed Mar. 22, 1968, Ser. No. 715,144

Int. Cl. A01n 9/22 US. Cl. 71-92 Claims ABSTRACT OF THE DISCLOSURE The present invention is concerned with methods and compositions useful in inhibiting the growth of plants, and is particularly directed to methods employing and compositions comprising an active agent which is a compound of the formula pound of the formula and its acid addition salts, wherein R, as above, represents halo or methyl, said R being located on the 6 or 7 position, only, and n represents an integer of from 0.

to 1, both inclusive.

DETAILED DESCRIPTION OF'THE INVENTION As above set forth, the present invention is concerned with methods employing and compositions comprising an active agent which is a compound of the formula ICC It is noted that certain compounds within the definition of active agent are tautomers:

For the purposes of the present invention, either tautomeric form of such compounds can be utilized,'or the compound can be employed as a mixture.

All of the compounds to be employed as active agent in accordance with the present invention are prepared by known procedures, and many of the compounds are commercially available.

In a first method, suitable for preparation of those compounds wherein R represents hydroxy, a phenylenediamine of the formula is reacted with benzoylformic acid:

The reaction, conveniently conducted in an inert liquid reaction medium and at reflux temperatures, results in the preparation of the corresponding 2-hydroxy-3-phenylquinoxaline. Such compounds can be converted to corresponding 2-halo compounds by the method of Shiho methyl, said R being located on the 6 or 7 position, only; R represents halo, hydroxy, loweralkoxy, amino, nloweralkylamino, di-n-loweral kylamino, or piperidino; and n represents an integer of from 0 to 1, both inclusive. The present invention is also directed to the novel compound of the formula et al. (Chemical Albstracts, 56, 1453b [1962]) wherein, in the preparation of 2-chloro-3-phenylquinoxaline, Z-hydroxy-3-phenylquinoxaline was refluxed with P001 For preparation of those compounds wherein R represents amino, loweralkylamino, diloweralkylamino, or piperidino, the corresponding 2-halo-3-phenylquinoxaline is reacted with a suitable amine to obtain the corresponding 2-amino, loweralkylamino, diloweralkylamino, or piperidino compound. The reaction requires the presence of a hydrogen halide acceptor for good results.

In a representative example, 7.2 grams of 2-chloro-3- phenylquinoxaline (0.03 mole) is added to and mixed with sodium hydroxide (1.2 grams; 0.03 mole), piperidine (2.5 grams; 0.03 mole), and 25 milliliters of dimethylformamide. The mixture is refluxed for several hours, with stirring, and then permitted to cool and poured onto ice. The 2-piperidino-3-phenylquinoxaline typically separates as a yellow gum; it is separated, washed with water, dried, and recyrstallized from petroleum ether. In a rep resentative operation, the product obtained melted at 82-4 C., and its structure was conrfirmed by NMR analysis.

Also, the 2-halo, especially 2-chloro compounds, can be used as starting materials to prepare the corresponding 2- loweralkoxy compounds. Such 2-halo compound is reacted with an alkali metal loweralkoxide, preferably in the same loweralkanol as solvent. The tautomers can be separated in known chemical procedures. Thus, for example, the mixture can be subjected to hydrolysis whereupon the reacting 2-loweralkoxy tautomer will be converted to the corresponding 2-hydroxy compound which can, in turn, be separated from the non-reacting l-loweralkyl-3-phenyl-2(1H)-quinoxalone tautomer. Chromographic separation can also be employed, especially for small quantities.

l Representative compounds'to be employed in accordanee with'the'p'resent inventioninclude: 2-chlor0-3-phenylquinoxaline Z-bromo-3 phenylquinoxaline 2-iodo-B-phenylquinoxaline 1 g 2-amino-3-phenylquinoxaline 2-hydroxy 3-phenylquinoxaline 2-ethoxy-3-phenylquinoxaline 2-fluoro 3:phenvlquinoxaline 2- methylamino-3-phenylquinoxaline 2-n-propylamino-3-phenylquinoxaline 2-dimethylamino-3-phenylquinoxaline 2-diethylamino-3-phenylquinoxaline v2,6-dichloro-3-phenylquinoxaline 2-chloro-7methyl-3wphenylquinoxaline 2-hydroxy-7-bromo-3 phenylquinoxaline 2-amino-6-fluoro-3-phenylquinoxaline 2-methoxy-6-iodo-3 -phenylquinoxaline 2-piperidino-6chloro-3 phenylquinoxaline 2-piperidino 7-rnethyl 3-phenylquinoxaline 2-dimethylamino-6 chloro-3-phenylquinoxaline Z-piperidino-7-brorno-3-phenylquinoxaline 2-chloro-3-phenylquinoxaline hydrochloride Z-hydroxy-3-phenylquinoxaline acetate 2-piperidino-3-phenylquinoxaline hydrochloride 1-methyl-3 -phenyl-2( 1H) -quinoxalone 2-piperidino-6-methyl-3-phenylquinoxaline 2-sec-butoxy-3-phenylquinoxaline 2-piperidino-6-fiuoro-3-phenylquinoxaline 1-ethyl-7-chloro-3-phenyl-2( lH),- quinoxalone 2-piperidino-7-iodo-3-phenylquinoxaline The compounds serving as active agent in accordance with the present invention, in'the base form, are crystali line solid substances. Generally, the free base is much preferred; many of the salts are less stable. Mixtures of one or more of the compounds can be used. The compounds are soluble in various organic solvents. They are advantageously adapted to be employed as agents for the inhibition of plant growth. Although the compounds can be utilized at high rates to achieve broad herbicidal activi ty, they can also be employed to take advantage of their selective pattern of activity, which is exhibited at lower rates, especially when employed in preemergent applicainhibition falling short of actual killing is adequate, par- 'ticula'rly when "combined with 'naturally occur-ring consuch as; for example, cotton, corn, sorghum, soybeans,

and the like. In suchuse, application can be made preemergent to both crops and weeds, or, preferably by means of a directed spray-application technique, postemergent to thecrop plant butboth preemergent'and postemergent to the weeds. In another application, the compounds can -be used to give broad herbicidal action on non-crop plant land,:includingintermittentlynon-crop strips of contour,- farmed land. For such usage on so-calledfallowland, application can be made in spring. to suppress vegetative growth until a fall orfollowing s'pring planting, or in the fall to suppress vegetative growth until a spring or following fall planting. Furthermore, in another application, the present compounds can be utilized to control Weeds in tree crop plantings, such as plantings-of the various citrus trees. In these latter types'of applications, the present compounds are particularly advantageous because of the relatively rapid disappearance of their herbicidal effect, thereby permitting subsequent crop plantings as in the instance of contour farming, and avoiding buildup in the soil. n

Thus, in particular embodiments, the present invention is directed to a method for inhibiting the growth of weeds in an area seeded 'or planted to a crop plant which comprises applying to the area an amount of active agent which inhibits the growth ofweed's without causing substantial harm to the crop plants, wherein the crop is .(a) corn, (b) soybeans, or. (c) sorghum. f V h In yet another particular embodiment, the presentin vention is directed to a'method for controlling the growth of vegetation in fallow land which "comprises applying to such land an effective amount of the active agent of the present invention.

The practice of the present invention in any of its numerous embodiments-can in some instances .be carried out with unmodified compound; however, for good re? sults, it is generally necessary that the compound be em- 1 ployed in modified form, that is, as one component of a compounds, exhibita different pattern of activities. They i exhibit, as the rest of the compounds to be employed in accordance with the'present invention, selective activity in preemergent application. But they are active in post emergent application, although with little selectivity, at Y; rates'below those rates at which the rest of the compounds to be employed as active agent are effective.

In. its broadest sense, the present invention is directed to a method which comprises applying to a plant part,

which can be 'a seed or other similar reproductive unit composition formulated to implement the plant growth inhibiting effects. Thus, for example; the active agent can be mixed with water or'other liquid or liquids, preferably aided by the usage of a'surfa'ce active agent. The active agent can also be'incorporated on a finely divided solid, which can be a surfaceactive substance, to yieldja 'wet: table powder; which can subsequently be dispersedin water. or other liquid, or a dust which can be applied directly. Other methods of formulation are known in the art and jcan be employed in implementing the present invention.

In carrying out the novel method of the present invention, the exact amount of the active agent employed is not critical and 'will vary, depending upon the type of growth-inhibiting effect desired, the identity of the plants crop plant which comprises applying to the area an amount of active agent which inhibits the growth of vegetation is merely inhibited. Especially in the practice of the present invention for obtaining selective action,

concerned, the particular active agent used, Weather conditions, and the like; In general, a broad growth-inhibiting effect is .obtained with "rates offrom 0.5 to '20 pounds or more of activeagent i per acre,'and preferably with rates of from 5 to 20 pounds or more, and such rates are suitable and effective for control of vegetative growth "on fallow land. When it is desired to obtain a selective growth-inhibiting effect on weedsin areas containing crop plants such as 'corn, soybeans, and cotton, rates of from 0.5 to 10 pounds generally give good'res'ults. The'Z-pip'erh dino compounds disclosed and claimed herein as new compounds generally give selective growth inhibition, in pro-emergent application, at rates of from pounds, and preferably at rates of from 7.5 pounds and higher per acre; postemergent activity with these compounds is exhibited at rates as low as 1 pound and lower, with some selectivity. When in the typical mode of'operation, the active agent is employed as a composition comprising the agent, the exact concentration of active agent in the composition is not critical, except that the concentration and total amount of formulation employed be adequate to supply the appropriate amount of active agent on a per acre basis. In general, good results are obtained when employing formulations. containing the active agent in a concentration of. from 0.5 to percent or higher, in the instance of a liquid formulation; and in a concentration of from 1.0 to 5.0 percent or higher, in the instance of a dust, powder, granule, or the like. More concentrated formulations can be prepared and are often preferred in that they can serve, depending upon the particular application contemplated and the particular concentration, both as a concentrated formulationfor purposes of shipment, storage, and the like, and as an ultimate treating composition. A preferred composition comprises a surface active agent, an inert finely-divided solid and the present active agent, the active agent being present in an amount of from 0.5 to 99.5 percent, by weight.

The expression surface active dispersing agent, as herein employed, is intended to include all agents which are capable of acting at' the interfacial surface between the active agent and Water or other liquid medium; facili- .tating' thereby thedispersion of the agent in the medium: The term is inclusive of solid emulsifying agents such as finely-divided bentonite, pyrophyllite, fullers earth, attapulgite, silica, other clays, and mineral carriers as well as liquid wetting and dispersing agents.

The term inert finely-divided solid, as herein employed, refers to materials whose primary function is not as dispersant of the active agent in a liquid medium but as carrier for dust compositions. Representative such materialsare chalk, talc, gypsum, powdered walnut shells,

etc.

Liquid, compositions containing the desired amount of active agent are prepared by dissolving the substance in an organic liquid or by dispersing the substancein water with or without the aid of a suitable surface active dis: persing agent such as an ionic or non-ionic emulsifying agent. Such compositions can also contain modifying substances Which serve as a fsprea derlf and sticker on plant foliage. Suitable organic liquid carriers include the agricultural spray -oils and the-petroleum distillates such as diesel .fuel, kerosene,.fuel oil naphthas and Stoddard sol.- vent...Among .such. liquids .the petroleum distillates are generally preferred, The aqueous compositions can con tain one or more water immiscible solvents for the toxicant compound. In .such compositions, the carrier com- .cohols and'the like. For a review of known surface active agents which iaresuitably'" employed 'in implementing the present invention, attention is directed to US. 3,095,299 second column, lines 2546, and references there cited.

In'the preparation of dust compositions, the active'ingredient is intimately dispersed inand on a finely-divided 'sol idsuch as' talc, chalk, gypsum, and the like. In one method of achieving such dispersion, the finely-divided carrier is mechanically mixed or ground with the active agent. I Similarly, dust compositions containing the toxicant compounds can be prepared with various of the solid surface active dispersing agents, such as bentonite, fullers earth, attapulgite, and other clays. Depending upon the proportions of ingredients, these dust compositions can be embloyed as concentrates and subsequently diluted with additional solid surface active dispersing agents or with chalk, talc, or gypsum and the like to obtain the desired amount of active ingredient in a composition adapted, to be employedfor the suppression of the growth of the plants. Also, such dust compositions can be dispersed in water, with or without the aid of a dispersing agent, to form spray mixtures.

Formulation-s containing the present active agent are often advantageously further modified by incorporation therein of an effective amount of a surfactant which facilitates the dispersion and'spreading of the formulation on the plant. leaf surfaces and the incorporation of the formulation by the plant.

In accordance with the present invention, the active agent can be dispersed in soil or other growth media in any convenient fashion. Applications can be carried out vby simply mixing with the media, by applying to the surface of soil and thereafter dragging or discing into the soil to the desired depth, or by employing a liquid carrier to accomplish the penetration and impregnation. The application of spray and dust compositions to the surface of soil, or to plant parts or the above ground surfaces of plants can be carried out by conventional methods, e.g., powder dusters, boom and hand Sprayers and spray dusters,whether surface or air-borne.

In a further method, the distribution of the active agent in soil can be accomplished by introducing the agent in the water employed to irrigate the soil. In such procedures, the amount of-water is varied with the porosity and water holding capacity of the soil to obtain a desired depth of distribution of the agent.

In addition, the present method also comprehends the employment of an aerosol composition containing one or more of the present active agents as an active compound.

Such a'composition is prepared according to conventional methods wherein the agent is dispersed in a solvent, and

the resultant dispersion mixed with a propellant in liquid state. Such variables as the particular agent to be used and the nature of the vegetation which is to be treated will determine the'desira'bility of the solvent and concentration of the agent therein. Examples of suitable solvents are water, acetone, isopropanoL'and 2-ethoxyethanol.

Satisfactory results are obtained when'the active agent of the present invention, or a composition comprising such active agent, is combined with other agricultural materials intended to be applied to plants, plant parts, "or their habitats. Such materials include fertilizers, fungicides, insecticides, other herbicides, soil conditioning agents, andthe like. i Where the present compounds are to be employed for selective weed control in corn, a particularly preferred formulation is one which" comprises the present active agent in a solution of nitrogemwith, optionally, other adjuvants also present. The nitrogen solution serves as a fertilizer for the corn crop, but also is initially effective as a contact herbicide. Inasmuch as the contact-herbicidal action is not selective, such a nitrogen solution is applied as a directed spray to avoid or limit crop damage. Typically, suchnitrogen solutions contain from'about 261t0 present compounds in combination with one or more other, known, herbicides. For example, a combination of one of the present compounds with a known herbicide may yield a herbicidal product which is less expensive, as for large-scale herbicidal purposes, than sole use of the present compound would be-with the combination being equally effective. In addition, there are circumstances where the herbicidal activity of a compound of the present invention complements that activity of a known herbicide, making a combination of the two substances particularly desirable from the standpoint of the herbicidal results obtained.

The identity of the known herbicide with which one or more of the present compounds is combined is not critical. Representative known herbicides with which a compound of the present invention can be combined include, for example, those known herbicides listed in the Herbicide Handbook of the Weed Society of America (W. F. Humphrey Press, Inc., Geneva, N.Y., 1967); however, others can also be used.

Moreover, while the particular known herbicide with which a present compound or compounds is combined is not critical, a particularly preferred combination is that of (1) One or more of the compounds to be employed as active agent in accordance with the present invention; and

(2) A phenoxy or substituted phenoxyalkanoic acid of the formula:

Y'- (I) -oz -oon wherein each of Y, Y, and Y" represents hydrogen, halo, or methyl, at least one of Y, Y, and Y" being halo; and Z represents alkylene of from 1 to 4, both inclusive, carbon atoms; or an ester or salt of said acid.

Preferred phenoxy or substituted phenoxyalkanoic acids are 2,4-dichlorophenoxyacetic acid:

O 15 Cl- OCHa- --OH and its salts and esters; and 2-methyl-4-chlorophenoxyacetic acids and its salts and esters.

The identity of the salt or ester, when such derivative form is employed, is not critical. In general, the salt or ester moiety is selected to confer higher water solubility or other desirable properties on the substance. Representative and suitable salts and esters include the alkali metal, ammonium, trimethylammonium, alkylamine, which can be monoalkylamine, dialkylamine, or trialkylamine, alkanolamine, which can be monoalkanolamine, dialkanolamine, or trialkanolamine, salts, and the alkyl, alkoxyalkyl, and alkenyl esters. Others, of course, can be used. Preferred alkylamine or alkanolamines are those containing less than about 25 carbon atoms. Representative such amines include methylamine, ethylamine, diethylamine, trimethylamine, monoethanolamine, triethanolamine, isopropanolamine, n hexylamine, morpholine, dimethylamine, N-allyl-1,3-propylenediamine. Preferred esters are those in which the ester moiety contains not more than about 25 carbon atoms; and yet more preferred are those containing not more than about carbon atoms.

Representative phenoxy and substituted phenoxyalkanoic acid compounds to be employed in such combinations include the following:

2,4-dichlorophenoxyacetic acid isooctyl 2,4-dichlorophenoxyacetate morpholine salt of 2,4-dichlorophenoxyacetic acid 2,4,5-trichlorophenoxyacetic acid isooctyl 2,4,5-trichlorophenoxyacetate methyl 4-chlorophenoxyacetate n-butoxy-n-propyl 2,4-dichlorophenoxyacetate trimethylamine salt of 2,4-dichlorophenoxyacetic acid n-butyl 4- (4-chlorophenoxy) butyrate ethyl 2-(4-chlorophenoxy) propionate 2,4-dichlorophenoxyacetic acid, sodium'salt 2,4,5-trichlorophenoxyacetic acid, potassium salt triethanolamine salt of 2,4-dichlorophenoxyacetic acid 2-methyl-4-chlorophenoxyacetic acid allyl 2-methyl-4-chlorophenoxyacetate 2-(2,4,5-trichlorophenoxy)acetic acid N-allyl-1,3-propylenediamine salt of 2,4-dichlorophenoxyacetic acid isooctyl 2-(2,4,5-trichlorophenoxy)propionate 2-(2,4-dichlorophenoxy) propionic acid isooctyl 2-(2,4-dichlorophenoxy) propionate n-hexylamine salt of 2-methyl-4-chlorophenoxyacetic acid 4-(2,4-dichlorophenoxy) butyric acid n-hexyl 4- (2,4-dichlorophenoxy)butyrate 4-(2-methyl-4-chlorophenoxy) butyric acid n-hexyl 4-(2,4,5-trichlorophenoxy)butyrate 4-(2-methy1-4-chlorophenoxy)butyric acid n-hexyl 4-(2,4,5-trichlorophenoxy)butyrate 2,4-dichlorophenoxyacetic acid, ammonium salt trimethylamine salt of 2-methyl-4-chlorophenoxyacetic acid Such phenoxy or substituted phenoxyalkanoic acids can also be employed as the corresponding anilide. Thus, for example, the compounds of the present invention can also be employed jointly with compounds such as 2-(2-methyl- 4-chlorophenoxy) -m- (trifiuoromethyl acetanilide and. 2- (2-methyl-4-chlorophenoxy)-o-chloroacetanilide. In addition, the active agent of the present invention is advantageously combined with substituted benzoic acid and benzonitrile herbicides, such as, for example, 3-amino-2,5- dichlorobenzoic acid, 2,5-dichloro-3-nitrobenzoic acid, 2- methoxy 3,6 dichlorobenzoic acid, 2 methoxy-3,5,6-trichlorobenzoic acid, and 2,6-dichlorobenzonitrile. Furthermore, the active agent of the present invention can be combined with yet other known herbicides, such as, for example, 4-amino-3,5,6-trichloropicolinic acid or its salts or other derivatives.

The following examples illustrate the present invention.

EXAMPLE 1 Various of the compounds to be employed as active agent in accordance with the present invention were evaluated for preemergent application to various species of plants. In this evaluation, a soil was prepared consisting of one part masonry sand and one part shredded top soil blended together in a cement mixer. One gallon of this soil was placed in a 25 x 35 cm. galvanized flat and was patted down with a bench brush until level. A three-row marker was used to make 2 /2 cm. deep furrows in approximately two-fifths of the flat. Crop seeds consisting of four kernels of corn, five cotton seeds and five soybean seeds were placed in these furrows. A four-row template was then placed on the remaining soil and the indicated amounts of each of the following seeds were planted, one species to each section: foxtail (millet), mg.; broad leaf mustard, 50-75 mg.; rough pigweed, 30-50 mg.; and large crabgrass, 350-400 mg.

Sufficient soil was added to cover the entire flat. Thus, the weed seeds were covered to a depth of about 6 mm. 3nd the crop plant seeds were covered to a'depth of about In assaying the effect of the composition as preemergent herbicides, a flat prepared as above, taken either on the day of planting or on the next day, was placed in a chamber equipped with a turntable and an air exhaust.

The herbicidal composition, either a spray-type emulsion or a wettable powder, was applied to the flat with a modified De Vilbiss atomizer hooked to an air source. Twelve and one-half ml. of the composition under test were applied to each flateither on the day of planting or the succeeding day. Injury ratings and observations as to type of injury were made eleven to twelve days after treatment. The injury rating scale used was as follows:

10 EXAMPLE 2 Representative compounds of the present invention were evaluated for post-emergent application to plants. Theevaluation was carried out in accordance with the procedures of Example 1 except that the test solutions were applied about 9-12 days after the preparation and seeding of the flats. The results are as set forth in the following table:

TABLE II.,IN.TURY RATING ON POST EMERGENT TREATMENT Lbs./ Cot- Soy- Crab- Mus- Pig- Foxtail Compound acre Corn ton beans grass tard weed millet 2-chloro-3-phenylquinoxaline 8 1 2 1 3 4 4 2 2-amino-3-phenyl- 8 0 0 2 3 3 1 2 quinoxaline- 4 0 1 2 2 1 1 1 2-piperidino-3-phenyl- 4 2 2 2 3 4 3 4 quinoxaline 2 1 l 1 2 4 3 2 0no in ury EXAMPLE 3 1slight injury 2-moderate injury 3severe injury 4-death 2-chloro-3-phenylquinoxaline was evaluated under field conditions. In this evaluation, field plots were prepared in routine fashion and a number of the plots divided into I two portions. One portion of each plot was seeded with of the following procedures. In one method, the particular compound was -wett'ed by grinding in a mortar with one part of polyoxyethylene sorbitan monolaurate. Five hundred parts of water were added slowly to the resultant creamy paste to give an aqueous dispersion with a surfactant concentration of 0.2 percent. This dispersion TABLE I.INJ'URY RATING ON PREEMERGENT foxtail and crabgrass (grasses); the other portion was seeded with pigweed. Other plots were seeded with corn, sorghum, and soybeans, and yet other plots were set aside as control plots. In the instance of the plots seeded with grasses and pigweed, treatment was by way of incorporation in the soil immediately preceding the seeding in the instance of one-half of each portion of such plot; in the instance of the other half, treatment was by means of a surface spray application immediately after seeding. In the instance of the plots seeded to cropplants, application .was exclusively by means of pre-plant incorporation. All plots were then held under good growing conditions for a period of several weeks, at which time readings were made of the degree of control.

The results of the evaluation are set forth in the following table, where herbicidal activity is rated from 0-10, 0 indicating no herbicidal eifect, and 10 indicating a killing of the vegetation in question. PPI is used to indicate application by pre-plant soil incorporation, and SS to indicate application by surface spray application immediately after seeding.

TREATMENT Lbs.l acre Cotton

Soybeans Compound Mus- Pig- Foxtail Velvet tard weed millet lea 2-hydroxy-S-phenylquinoxaline- 2-chloro-3phenylquinoxaline 2- (dipropylamino)-3-phenylquinoxallne 2ethoxy-3-phenylquinoxaline 2-hydroxy-7-methyl-3-phenylquinoxaline 2-hydroxy-fi-methyl-S-phenylqulnox no 6-chloro-2-hydroxy-3-phenylquinoxaline 7-0hloro2-hydroxy-3-phenylqu1noxaline l-methyl-3-phenyl-2-(1H)-quinoxalone 2-methoxy-3-phenylquinoxaline- 1-n-propyl-3-phenyl-2-(1H)-quinoxalone 2-n-propoxy-3-phenylquinoxaline..-{

2-amino3-phenylquinoxaline 2-piperidino-B-phenylquinoxaline NWNCADWI-ILQOJWNNWN 1 WEED CONTROIJ RATING-INJ'URY RATING Grasses Plgweed Crops (all PPI) Sor- Soy- Lbs/acre PPI SS PPI SS Corn ghum beans Iclaim:

1. The method which comprises applying to a plant part a growth-inhibiting amount of an active agent, said active agent being a compound of the formula til- 3 or its acid addition salt, wherein R represents halo or methyl, said R being located on the 6 or 7 position, only; 7 1

or its acid addition salt, wherein R represent halo or methyl, said R being located on the 6 or 7 position, only;

R represents halo, hydroxy, loweralkoxy, amino, n-loweralkylamino, di-n-loweralkylamino, or piperidino; and n represents an integer of from 0 to 1, both inclusive, further limited in that the term halo designates bromo, chloro, fluoro, or iodo, only.

3. The method of claim 2 wherein the active agent is 2-chloro-3-phenylquinoxaline.

4. The method of claim 2 wherein the active agent is 2-hydroxy-3-phenylquinoxaline.

5. The method of claim 2 wherein the active agent is 2-methoXy-3-phenylquinoxaline.

6. The method of claim 2 wherein the active agent is 2-piperidino-3-phenylquinoxaline.

7. The method of claim 2 wherein the active agent is 2-amino-3-phenylquinoxaline.

8. The method of claim 2 wherein the crop plant is com.

9. The method of claim 8 wherein the active agent is 2-chloro-3-phenylquinoxaline.

10. The method of claim 8 wherein the active agent is 2-hydroxy-3-phenylquinoxaline.

References Cited Jones 71--117 LEWIS GOTTS, Primary Examiner C. L. MILLS, Assistant Examiner US. Cl. X.R. 260-250R 

